Racehorses competing on tracks in California tended to run slower on days when the air quality was worse, specifically at levels far below what the federal government currently considers safe for humans, according to new Colorado State University research published recently in the Equine Veterinary Journal.

“It’s concerning, the idea that we can look at daily fluctuations in air quality and see meaningful impacts on animal athletes,” said Sheryl Magzamen, an environmental health scientist in CSU’s College of Veterinary Medicine and Biomedical Sciences who studies the effects of air pollution on respiratory health and is the study’s lead author.

The findings establish a relationship between air quality and athletic performance in horses on a scale that has not been done before, Magzamen said. The work could also have implications for better understanding the impact of air pollution on human athletes.

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Magzamen and her co-authors gathered horse racetrack data from more than 30,000 races at 12 tracks in California between 2011 and 2020. They also gathered information from nearby air monitors operated by the U.S. Environmental Protection Agency. In comparing the two datasets, the researchers had a unique opportunity to examine how different levels of pollutants, including ozone pollution and PM2.5, affected racehorse performance. (PM2.5 refers to harmful particles in the air that are smaller than 2.5 micrometers in diameter; scientific studies have linked these particles to numerous health problems, including heart disease, asthma and low birth weights.)

COLLABORATION

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Magzamen collaborated on the study with CSU veterinarians, including professor Dr. Colleen Duncan, preventative medicine resident veterinary Dr. Danni Scott and former CSU master’s student Linda D. Kim.

“I wouldn’t necessarily have thought to put these two things together,” said Magzamen, who credits Duncan with the idea to harness the information from the racehorse tracks, “but it’s been really interesting.”

Notably, the study’s authors found that horse speed was negatively impacted by concentrations of PM2.5 far below what the EPA currently considers the upper limit for “good” air quality. The differences were small, fractions of a second, but still statistically significant, Magzamen said. However, according to the study, the relationship was not strictly linear; the study did not find that significantly higher concentrations of PM2.5 slowed down the horses.

Earlier this year, the EPA lowered the level pf PM2.5 it considers safe, from 12 micrograms per cubic meter of air to 9. The EPA reviews the standard every five years, and it was the first year since 2012 that the agency tightened the guidance. According to the Equine Veterinary Journal study, horses were adversely affected by concentrations as low as 4 micrograms per cubic meter.

“We usually talk to people who are, rightly so, worried about their own health,” Magzamen said. “This work is important because it’s a wake-up call for what’s going on with our animals as well.”

As a public health expert, Magzamen said she is more concerned about the health impacts on days where it is less obvious that there are harmful pollutants in the air — the kinds of days where the racehorses were statistically slower. “Days where it may look a little hazy, but it’s not associated with an emergency response,” she said. “Those are the days that we’re worried about most because there isn’t necessarily a strong visual or sensory cue to that drives people inside.”

MILK PRODUCTION IMPACT

This new paper builds on work that Magzamen, Duncan and others co-authored in 2022 showing that dairy cattle that were exposed to high levels of PM2.5 made less milk, and the milk that they did produce contained higher levels of inflammatory markers that can signal other health problems.

It was difficult, however, to expand on the initial results with the dairy cattle, Magzamen said, because additional air pollutant information was challenging to find. In the case of the racehorses, multiple California racetracks happened to have EPA air monitors within a few dozen miles. What’s more, California has horseraces year-round, so in both cases the necessary data was abundant and could be closely studied.

Scott, who is a fellow with the Morris Animal Foundation and pursuing her doctoral degree in epidemiology, is already in the process of expanding on this new work. She is looking at whether there is a difference in performance between horses that trained on days when the air was polluted compared to those that trained on clean-air days by examining pre-competition training data. “This initial work is really interesting and sets up the case for what I’m working on now, taking it one step further,” she said. “It’s a little bit like piecing a puzzle together.”

Magzamen hopes that the study can help better inform horse owners about the potential negative impacts air pollutants can have on those animals, and also eventually help researchers better understand the implications for human athletes. She is looking into whether she might be able to replicate a similar study for humans by examining data from high school track meets.

“Right now, you can check the air quality on your phone,” Magzamen said. “But the challenge for us working in public health is that what we tell people to do after that is so dependent on your demographics and if you’re managing a chronic illness. If you’re an athlete and you’re trying to exercise we don’t have good advice right now about what to tell you other than, ‘If you start feeling bad, stop running or biking or hiking.’ Hopefully we can change that.”